JPH0651600A - Copying device - Google Patents

Abstract

PURPOSE:To stabilize an image by preventing an image from being changed caused by a characteristic change by the temperature change of a photosensitive body just after supplying power by controlling timing to perform image correction operation in accordance with the temperature of the photosensitive body. CONSTITUTION:The photosensitive body 2 is heated by a drum heater 27 when the power is supplied. The temperature of the photosensitive body 2 is detected by a photosensitive body temperature detecting sensor 57 and is supplied to a CPU. The CPU judges whether the temperature of the photosensitive body 2 is 30 deg.C in the case that the temperature of a fixing device 4 inputted from a fixing temperature detecting part exceeds 70 deg.C. Then in the case that the temperature of the photosensitive body 2 is >=30 deg.C, the CPU controls to execute setting a process condition(electrostatic charging potential of photosensitive body 2) by a test mode at every two hours. Also in the case that the temperature of the photosensitive body 2 is <30 deg.C, the CPU controls to execute setting the process condition by the test mode at every 10 minutes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, and more particularly to a copying machine capable of full color copying.

[0002]

2. Description of the Related Art Conventionally, some copying machines capable of full-color copying have an image correction function for stabilizing an image.

The following are examples of this image correction function. That is, a density detecting sensor using infrared light is provided in the copying apparatus to detect the image density on the photoconductor or the transfer intermediate in the test mode. Then, the detected image density value [hereinafter, simply referred to as image density] and a preset reference density value [hereinafter,
Referred to as a reference density], and the process conditions (charging potential, exposure light source voltage, etc.) are changed and set so that the detected density has the same value as the reference density.

[0004]

The above-mentioned image correction function is generally carried out at the following timing.
That is, first, when the power is turned on, the fixing temperature is detected, and when the fixing temperature is equal to or lower than a predetermined temperature, it is determined that the power is initially turned on, and the image correction operation is performed. Next, the above-described image correction operation is performed every time a fixed time elapses.

However, since the photoconductor used in the copying machine has a large characteristic change with respect to environmental conditions, particularly temperature, it is exposed by the heat source in the machine until a certain period of time elapses after the power is turned on. When the body temperature rises, the characteristics of the photoconductor also change accordingly. As a result, there is a problem in that image variation may occur.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a copying apparatus capable of controlling the timing of an image correction operation based on the temperature of a photoconductor. is there.

[0007]

In order to solve the above-mentioned problems, the present invention comprises means for detecting the temperature of a photoconductor, and means for controlling the timing of performing an image correction operation according to the detected temperature of the photoconductor. It has a configuration with.

Further, in the present invention, when the power is turned on, the photoconductor is heated, the temperature of the photoconductor is detected, and the image correction operation is performed at a predetermined timing until the temperature reaches a predetermined temperature. It can be configured to.

[0009]

When the power is turned on, the photoconductor is heated and the temperature of the photoconductor is detected.

Until the temperature of the photoreceptor reaches a predetermined temperature,
The image correction operation is performed at the first timing with a short time interval. Then, after the temperature of the photoconductor reaches a predetermined temperature, it is performed at the second timing, which is a time interval longer than the above-mentioned first timing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the configuration of the main part of a copying apparatus to which the present invention is applied.

In the structure of FIG. 1, a document table 61, a light source 63 for exposing a document, a mirror,
An optical system 6 including a lens and a color separation filter is provided. Further, a drum heater 27 and a photoconductor 2 having a photoconductor temperature detection unit 57 are provided substantially in the center of the copying machine main body 1. Around the photoconductor 2, a charging charger 21,
The blank lamp 22, the developing devices 23a to 23c, the transfer body 24, the cleaning device 25, and the charge eliminating lamp 26 are arranged in the order described above.

The charging charger 21 uniformly charges the surface of the photosensitive member 2 by generating corona discharge, and the charging potential of the photosensitive member 2 is adjusted by changing the voltage applied to the charger wire. The blank lamp 22 is the photoconductor 2.
The surface of the photoconductor 2 uniformly charged by the charging charger 21 is partially exposed to partially cancel the charge on the surface of the photoconductor 2.

The developing devices 23a-23c are loaded with yellow, magenta, and cyan toners, respectively, and any one of them is used in the test mode for setting process conditions.

The cleaning device 25 removes the toner remaining on the photoconductor 2, and the charge eliminating lamp 26 removes the charging potential remaining on the photoconductor 2.

The drum heater 27 is an electrothermal type heater capable of arbitrarily controlling the temperature of the photoconductor 2, and is arranged inside the photoconductor 2. Further, the photoconductor 2 is provided with a photoconductor temperature detection sensor 57 described later.

FIG. 2 is a diagram showing the relationship between the charging potential of the photoconductor 2 and the temperature of the photoconductor 2, and FIG. 3 shows the relationship between the temperature of the photoconductor 2 and the time required to reach each temperature. It is a figure. As is clear from FIG. 2, the characteristics of the photoconductor 2 enter the stable region LO1 when the temperature of the photoconductor 2 is 30 ° C. or higher. As is clear from FIG. It takes about 20 minutes to reach the temperature of 30 ° C. indicated by Lth.

Returning to FIG. 1, the description will be continued. Transfer body 2
Reference numeral 4 denotes a dielectric sheet stretched between three rollers and rotated at the same speed as the peripheral speed of the photoconductor 2. The photoconductor 2 is brought into contact with the transfer body 24, and a first transfer roller (hereinafter referred to as 1st transfer roller) 24a is disposed at the abutting position, and the toner on the photoconductor 2 is transferred to the transfer body 24. It Transfer body 2
A second transfer roller (hereinafter, referred to as a 2nd transfer roller) 24c, a peeling plate 24d, and a cleaning device 24e are arranged around the periphery of No. 4 in the above order.

The 1st transfer roller 24a transfers the toner on the photoconductor 2 to the transfer body 24, and the 2nd transfer roller 24c transfers the toner on the transfer body 24 to the sheet, and the peeling plate 2
4d removes the paper, and the cleaning device 24
The e removes the toner remaining on the transfer body 24.

A toner sensor (density detector) 24b is arranged downstream of the first transfer roller 24a so as to face the transfer body 24. The toner sensor 24b is a reflection type optical sensor, and the toner sensor 24b has the characteristics shown in FIG.
The toner density on the transfer body 24 is detected by voltage. The toner sensor 24b detects the toner density of a specific density area formed on the transfer body 24 in the test mode described later.

FIG. 5 is a diagram showing a method of detecting the density of a specific density range by the toner sensor 24b. Solid lines in the drawing represent the densities of the specific density regions 7a and 7b and the transfer body 24. As shown, the densities in the specific density regions 7a and 7b are not flat but have variations. In particular, due to the edge effect of the electric field, a large amount of toner is attached to the image leading end portion to increase the density, and the toner is less likely to be attached to the image trailing end portion to decrease the density. The toner sensor 24b has a specific density range 7a.
In the intermediate portion excluding the image leading end portion and the image trailing end portion in (7b), toner density detection is performed n times. An average value is obtained by the CPU, which will be described later, from the results of toner density detection performed n times, and the result is used as the toner density.

In the specific density range, the uniformly charged photoconductor 2 is exposed by the blank lamp 22, and the developing devices 23a to 23a.
It is formed by attaching toner by any of 3c. The charging potential of the photoconductor 2 (voltage of the charging charger 21) is switched in about three stages during one rotation of the photoconductor 2, so that three types of specific density regions are formed in one process. In the test mode, since the blank lamp 22 performs the exposure, the exposure amount is always constant. Therefore, the toner density in the specific density range depends on the charging potential of the photoconductor 2.

FIG. 6 is a diagram showing the relationship between the charging potential of the photoconductor and the toner density in a specific density range formed. As can be seen from the figure, under each environmental condition (temperature, humidity), when the photoconductor charging potential is in the region B, the toner concentration is almost saturated, so that the toner concentration does not change even if the photoconductor charging potential changes. Shows almost no difference. However, when the photoconductor charging potential is in the area A, the toner density changes according to the photoconductor charging potential. Therefore, if the photoconductor charging potential is selected within the area A, the toner density can be accurately detected according to the photoconductor charging potential.

The range of this area A is 420 to 580.
It is about V, and in the test mode, the charging potentials (voltages of the charging charger) of about three types of photoconductors are set as process conditions within this range, and a specific density range is formed.

By setting the voltage of the charging charger, the toner density of the toner adhered in the specific density range can be determined by the toner sensor 24b.
Detected by. In this embodiment, the charge potential of the photoconductor 2 is set as the process condition in the test mode, and the charge potential of the photoconductor 2 is set as the process condition in the image forming mode by detecting the toner density in the specific density range in the test mode. can do. However, when a good image is formed by the copying apparatus, it is not enough to set the charging potential of the photoconductor 2. Photoconductor 2 set there
The exposure amount of the lamp of the light source 63 of the optical system is also set in accordance with the charging potential of. As a result, the halftone of the original can be reproduced well.

FIG. 6 also shows the relationship between the photoconductor charging potential and the toner concentration when the temperature and humidity of the environment change. It can be seen that the toner concentration of (the toner concentration of the formed image) changes. Therefore, if the toner density in the specific density range is detected and the process conditions such as the charging potential of the photoconductor are set according to the toner density, a good image can be formed regardless of environmental changes.

FIG. 7 is a diagram showing the relationship (gamma characteristic) between the original image density and the copy image density when the charging potential of the photoconductor is changed, and FIG. 8 is the original document when the exposure amount of the light source 63 is changed. It is a figure showing the relationship (gamma characteristic) between density and copy image density.

In FIG. 7, when the voltage of the charging charger is increased, the charging potential of the photoconductor is increased as a whole. Therefore, if the exposure amount remains low, the residual potential level (potential of the exposed portion) becomes high and the density in the low density region also becomes high, resulting in a high contrast image. In FIG. 8, when the exposure amount of the original is increased, the amount of charge cancellation in the low density region of the original is almost unchanged. Therefore, when the exposure amount is increased, the image density in the low density region becomes light and the image becomes hard. To be prevented.

FIG. 9 is a diagram showing the relationship between the correction amount of the charging potential of the photoconductor and the correction amount of the exposure amount obtained from the above, and the correction amount of the charging potential and the correction amount of the exposure amount are in a substantially proportional relationship. . At the beginning of use of the photoconductor, the developer, etc., it is not necessary to correct the charging potential and the exposure amount, so the correction amount is
Which is the reference value.

Next, the control unit of the copying machine will be described with reference to FIG. In the configuration of FIG. 10, a ROM 41, RA
M42, I / O 45, 46, 47, 55, etc. are connected. Further, although not shown, a key switch for inputting a control command is connected to the CPU 40.

The CPU 40 is connected to the fixing temperature detecting section 51 via the I / O 45, and the fixing temperature detecting section 51 is connected to the fixing temperature detecting section 51.
The fixing temperature information detected in step 4 is input to the CPU 40.
The CPU 40 is connected to the photoconductor temperature detection sensor 57 via the I / O 55.
The temperature information of the photoconductor 2 detected in step 3 is input to the CPU 40 via an amplification stage (not shown).

The CPU 40 is connected via an I / O 47 to a transfer body toner concentration detecting section 59, and the toner density information of the transfer body 24 detected by the toner sensor 24b of the transfer body toner concentration detecting section 59 is stored in the CPU 40. Entered in.

The CPU 40 is connected to the surface potential controller 48 and the copy lamp controller 49 via the I / O 46. The CPU 40 controls the surface potential control unit 48 and the copy lamp control unit 49 to cause the charging charger 2 to operate.
1. Drive the light source 63. Therefore, the charging potential of the photoconductor 2 and the voltage of the light source 63 that exposes the document are controlled. In addition, the blank lamp 2
It is also possible to control the exposure level of 2.

The operation of the copying machine will be described below. When the power is turned on, the photoconductor 2 is heated by the drum heater 27, and the temperature of the photoconductor 2 is detected by the sensor of the photoconductor temperature detection sensor 57. Photosensitive member 2 detected
Is supplied to the CPU 40 via the I / O 55.

In the CPU 40, if the temperature of the photoconductor 2 is 30 ° C. or less, the process condition setting is set to 1 as described later.
Control is performed every 0 minutes, and if the temperature exceeds 30 ° C., the process condition is set every 2 hours.

The original table 6 during the copying process in the image forming mode
The original is scanned on the sheet 1, and the reflected light is guided to the exposure point P on the photoconductor 2. A paper feed unit 3 including a paper cassette is provided on the right side of the copying machine main body 1, and paper is fed to the position of the second transfer roller 24c.

Toner is transferred to this paper by the second transfer roller 24c, fixed by the fixing device 4, and then discharged to the paper discharge tray 5.

An output signal from the fixing temperature detector 51 is input to the CPU 40 via the I / O 45, and the temperature of the fixing device 4 is obtained. The fixing device 4 has a heat roller, the surface temperature of which is detected by a temperature sensor (not shown), and the heater is controlled according to the detection. The surface temperature of the heat roller is controlled to a hundred and several tens of degrees during use, but if left unused for a long time, it will drop to about ambient temperature.

The CPU 40 has a toner sensor 24.
The detection result of b is the toner concentration detection unit 59 of the transfer member, I / O4.
It is input via 7. As described above, the toner sensor 24b performs detection n times for each specific density range 7a (7b) and inputs the result to the CPU 40. The CPU 40 calculates the average of the detected values of n times and sets the value as the toner density, and based on the calculated value, the charging potential of the charging charger 21 (charging potential of the photoconductor) and the exposure amount of the light source 63 are set. The set value is output to the control units 48 and 49 of.

The relationship between the charging potential correction amount and the exposure amount correction amount shown in FIG. 9 is stored in the RAM 42, and the charging potential of the photoconductor 2 and the exposure amount of the light source 63 are determined according to the detection result of the toner sensor 24b. Is corrected. The RAM 42 also stores the standard toner density S0 attached to the transfer body 24. The standard toner density S0 is set to 500V as the process potential in the image forming mode at the initial use of the photoconductor and the developer, and the blank lamp 22 is used for exposure at room temperature and normal humidity. The toner concentration detected by the toner sensor 24d when the specific concentration range is formed by the toner sensor 24d.

11 and 12 are flowcharts showing the processing procedure of the copying machine stored in the ROM.
First, when the power of the copying machine main body is turned on, the initialization of the memory and the preliminary operation processing are performed at n1, and the warm-up (heating) of the photoconductor 2 and the fixing device 4 is started. If the temperature T of the fixing device 4 is 70 ° C. or less, it is assumed that the fixing device 4 is left unused for a long time, and the process proceeds to n3 to proceed to the test mode in which the charging potential (voltage of the charging charger) of the photoconductor is set.

The test mode performed in n3 to n14, that is, the process condition setting will be described below. First, at n3, the charging potentials VD1 to VD3 of the photoconductor are set as the process conditions of the test mode. The charging potential of the photoconductor is, for example, VD1 = 500V, VD2 = 520V, VD3 = 48.
Three kinds of conditions of 0V are set. Note that the ease with which toner adheres under these conditions is set such that VD1 is an intermediate value and VD2 and VD3 are above and below this intermediate value VD1.

At n4, the photoconductor is charged and exposed by the blank lamp 22 under the three process conditions to form a specific density range, and the process conditions VD1
The toner densities S1 to S3 under VD3 are detected. As described above, the toner densities S1 to S3 are average values obtained by several detections in each of the specific density regions, and are the average values obtained without being affected by variations in toner adhesion and the edge effect of the electric field. You can get the exact value.

The toner densities S1 to S3 are compared with the standard toner density S0 stored in the RAM 42 (n5, n
6, n7), a process condition (charging potential) at which a toner density (any of S1 to S3) that is close to the standard toner density S0 is obtained is set as a process condition in the image forming mode (n8 to n10). However, the obtained toner concentration S1
When ~ S3 is largely deviated from the standard toner concentration S0, process conditions VD1 'to VD3' (n13) in which more toner is attached than the process condition set in n3, or process conditions in which less toner is attached VD1 ″ ~ V
D3 ″ (n14) is set.

In this case, as in the case of setting n3, VD1 'or VD1 "is set as an intermediate value, VD2' or VD2" is set as an upper limit value, and VD3 'or VD3 "is set as a lower limit value. , VD1 '= 560V, VD2' = 58
0V, VD3 '= 540 is set, VD1 "= 440V,
VD2 ″ = 460V and VD3 ″ = 420V are set.

The toner density detection process is performed again according to these three kinds of process conditions (n4). If the detected toner densities S1 to S3 are close to the standard toner density S0, the process conditions (photoreceptor) 2 charge potential)
Is set as a process condition in the image forming mode. In the test mode, the surface potential of the photoconductor 2 is set to be slightly lower in order to form a specific density region having a density slightly lower than the saturation density as shown in the area of FIG. 6A. When setting the charging potential, it is set higher than the charging potential set in the test mode.

At n15, the exposure amount of the light source 63 of the optical system is set based on this charge value from the relationship shown in FIG. If the toner density similar to the standard toner density S0 is not obtained even after the process condition setting is performed twice, it is determined that there is some error such as a defective charge value and error processing is performed.

In the test mode as described above,
If the process conditions in the image forming mode are set, n
Returning to step 16, the sensors and keys are read, and if any input is performed (n18), the process corresponding to the input is performed, but no input is performed. If the temperature falls below 70 degrees (n2), (n3)
Then, the process conditions are set as described above. For example,
If the input is a print switch (n18), (n1
The copying process is performed under the process conditions set in 9).

At n2, when the temperature of the fixing device 4 exceeds 70 degrees, it is judged whether the temperature of the photoconductor 2 is 30.degree. If the temperature of the photoconductor 2 is 30 ° C. or higher, the process condition setting in the test mode is 2
It is controlled by the CPU 40 so as to be executed every hour. Further, when the temperature of the photoconductor 2 is lower than 30 ° C., the CPU 40 controls so that the process condition setting in the test mode is performed every 10 minutes.

As described above, when the temperature of the photosensitive member 2 heated by the drum heater 27 is lower than 30 ° C., 10
Set the process conditions in the test mode every minute,
When the temperature is 30 ° C. or higher, the process condition is set in the test mode every two hours, so that the image change caused by the characteristic change due to the temperature change of the photoconductor 2 immediately after the power is turned on can be improved and the image stabilization can be performed. I can do it.

Further, in this embodiment, the copying machine is explained as an example, but the invention is not limited to this.
That is, any device having a function of forming an electrostatic latent image using the photoconductor 2 and directly or indirectly attaching toner to the electrostatic latent image to print out the image can be applied. .

In this embodiment, the charging potential of the photosensitive member (voltage of the charging charger) and the exposure amount (voltage of the light source 63 for exposing the original) are shown as an example of the process conditions. Etc. may be used as the process condition.

[0053]

According to the present invention, there is an effect that it is possible to prevent the image change caused by the characteristic change due to the temperature change of the photoconductor immediately after the power is turned on, and to realize the image stabilization.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of an embodiment of a copying apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a charging potential and a temperature of a photoconductor in the apparatus of FIG.

FIG. 3 is a diagram showing the relationship between the temperature of the photoconductor in the apparatus of FIG. 1 and the time required to reach each temperature.

FIG. 4 is a characteristic diagram of a sensor in the apparatus of FIG.

5 is a diagram for explaining detection of toner density in the apparatus of FIG.

6 is a diagram showing a relationship between toner concentration and charging potential according to environmental changes of the apparatus of FIG.

7 is a diagram showing a relationship between image density and document density when the charging potential of the apparatus of FIG. 1 is used as a parameter.

8 is a diagram showing the relationship between the image density and the document density when the exposure amount of the apparatus of FIG. 1 is used as a parameter.

9 is a diagram showing a relationship between a potential correction amount and an exposure correction amount of the apparatus of FIG.

FIG. 10 is a block diagram of a control unit of the apparatus of FIG.

11 is a flow chart illustrating the operation of the apparatus of FIG.

FIG. 12 is a flow chart illustrating the operation of the apparatus of FIG.

[Explanation of reference numerals] 2 photoconductor 21 charging charger 22 blank lamp 24 transfer body 27 drum heater 40 CPU 57 photoconductor temperature detection unit

Claims (2)

[Claims] 1. A copying machine having an image correction function, comprising: a means for detecting the temperature of a photoconductor; and a means for controlling the timing of performing an image correction operation according to the detected temperature of the photoconductor. Copying device characterized by. 2. The copying apparatus according to claim 1, wherein when the power is turned on, the photoconductor is heated, the temperature of the photoconductor is detected, and the image correction operation is performed in a predetermined manner until the temperature reaches a predetermined temperature. A copying machine characterized by being controlled so as to be executed at a timing.